Thermal stability analysis of DC-sputtered AL2O3 films for surface passivation of C-Si solar cells

Aluminum oxide (Al2O3) is well known as a good candidate for surface passivation of c-Si Solar cells for both n-type and p-type Si due to its very high negative fixed charge density (Qf ~1012-1013 cm -2) in combination with a low level of interface state density (Dit). This paper assesses the study of passivation quality of Al2O3 deposited by DC-magnetron sputtering in reactive mode. MOS-capacitors has been fabricated and characterized to extract the interface trap charge densities at the silicon/Al2O3 interface and effective charge in the dielectric. Lifetime measurements were also performed with quasi-steady-state photo-conductance decay, transient techniques to extract surface recombination velocity (SRV). The thermal stability of the film has been investigated in different atmosphere conditions to better understand passivation mechanisms involved. At the end, an optimum firing temperature and conditions are proposed to reach high quality surface passivation and avoiding blisters formation.